New Threat to London 2012: Poisonous Caterpillars Oak processionary moth caterpillar can cause quite a bit of distress By Evann Gastaldo, Newser Staff Posted May 1, 2012 8:08 AM CDT 9 comments Comments A caterpillar, but not the poisonous kind. (AP Photo/Dean Fosdick, File) (Newser) – Planning to attend the Olympics in London this summer? It's sure to be a fun time, except for the creepy-crawly detail of poisonous caterpillars that have been ravenously chomping on Britain's oak trees. The caterpillar in question is the larval form of the oak processionary moth, and its 63,000 toxic hairs can cause asthma attacks, skin and throat rashes, runny eyes, vomiting, and dizziness if inhaled, the Telegraph reports. The caterpillars originally came to London on oak trees imported from Holland in 2006, and authorities have been unable to halt their rapid spread across Britain. Recent mild winters have allowed their numbers to swell even further. "You can slow them down, but we will never find them all," says one arboretum head. "They will always keep increasing."